Treatment of acid tars



Sept. 14, 1948. R. J. MILLER TREATMENT oF Actu TA1-as Filed Aug. 2; 1945 m5. omi-29mm SOLVENT f 1v msmLmq coLuMN I1u7eno1 ROBERT L. MILLER Aomeys i sludges.

Patented Sept. 14, 1948 TREATMENT oF Aon) TABS Robert J. Miller, Berkeley, Califmassgnor to California Research Corporation, San Francisco, Calif., a corporation of Il)elaware,``

i Application August 2,1945,seria1No..6os,4s9

This invention relates to a method for the treatment `oi emulsined acid tars and particularly to the demulsication of such tars and to the production of acid free tars therefrom,

:V It is an `object of this invention to provide a 'method for the production of acid free tars.

It is a further object of this invention to pro- .videpa process for the4 demulsification of acid tars..

It is still another vobject of this invention to provide a method for the separation of emulsi- :Iied `acid tars into a tar fraction and an acid fraction. I

In accordance with these and other` objects whichjwill be obvious to those skilled in the art frointhe disclosure given, this invention consists in a process for the deaciclication of emulsied tars resulting from the hydrolysis of sulfuric acid This process is based on the discovery that; these extremely complex emulsified tars fmay be readily separated into an acid layerpand a tar layer by diluting the tar with a liquid having a high solvent power, filtering to remove the 'smallamount of solid material present, separating the filtrate into a tar layer and anacid layer veither by stratilication or by centrifu'ging, which tar layer may be treated to produce an acid tai'.

The accompanying figure shows a flow diagram illustrating the process of this invention. Emulfsied tar from hydrolized sludge is fed from free `tank I to mixer `'II where it is diluted with a solvent from tank I2.

The tar andV solvent are intimately mixed with or without the addition of the lter aid and are then `fed to lllter I3. The solid'material (lter cake) is removed from the filter va line I4 and the iiltrate is withdrawn via line I6 to settling tank Il. The filtrate is alllowed to stratify. 'Ihe aqueous acid layer is removed via line I8 and the tar layer is removed via line I9 to neutralizing tank 2|. Any acid remaining in the tar layer at this point is "neutralized with dilute caustic from tank 22.*, An aqueous layer is allowed to separate and is removed via. line 23, and the substantially neutral tar is removed to still 25 via line 26. The tar is now freed of solvent by distillation and the solvent may be recirculated Yto solvent tank I2 via line 2l. Deacidified tar is removed from the still via line 28.

The sludge resulting from the treatment of fsuch vstocks as straight run gasoline, kerosenes,

crackednaphthas and reformed naphthas may .be

4 claims (cli 1357148) acid layer andan emulsified tarlayer. The process of this invention deals `with the treatment of this emulsied tar layer.

` VAn emulsied tar subject t0 treatment by this method is one which contains up to about 75% by volume of dilute sulfuric acid in the form of an emulsion. These tars will settle only very slowly and incompletely if at all, and even with extreme mechanical working of the tar only about half of the acid phase can be separated.. Prolongedheating at elevated temperatures with and without additional water or solvents such as bendzene and cresylic acids does not serve to break the emulsion and allow ready separation.

It has been found that these tar emulsions contain a small amount of a solid insoluble ma terial. It has further been found thatthis solid material usually present in an `amount! between about 6% `and about 10% in the tars ldescribed above, ,may be readily removed by iiltration after dilution witha good solvent. t t t These tars are atbest only slightly soluble in aliphatic, naphthenic or oleinc hydrocarbons, and such solvents as butyl alcohol, Cellosolvfe,V tur'- pentine and acetone are not satisfactory solvents Vfor these tars. .It has been found, however, that highly'aromatic liquids are excellent solvents 'for these tars. For example,` benzene, toluene,xy lene and the like are excellent solvents when substantially pure, areY satisfactory if ina 60 to`70% aromatic `mixtureand are useable in a mixture containing only `of aromatics. Halogenated aromatic compounds are likewise suitable. 4Or ganic sulfides and such powerful solvents as chloroform are satisfactory, although a highly aromaticsolvent is preferred. Not all of the tar is soluble in any of these solvents and a small amount of a thick emulsion layer will very slowly settle if the mixture is not processed in a reasonable length of time.

^ Attempts have been made to break this complexlemulsion by treating the tar with benzene, and with such common emulsion breakers as alcohol, ferrie chloride, phosphoric acid, vcontact clay, and heat. These treatments were however without effect.

However, it h-as been discovered that when the tar diluted with a good solvent is filtered and `the small amount of solid material eiectively removed, the ltrate will separate in a reasonably short time. This filtration is preferably conducted with the addition of a lter aid such as Johns-Manville Celite No. 535 in order to prevent plugging of the pores ofthe lter, Vbut this procedure isV not essential to the operation of this process. Filtration may be carried ut at room temperature or if desirable, slightly elevated temperatures may be used. A feed rate of about 2 to about 6 barrels of tar per day per square foot of filter area has been found satisfactory, but the rate of feed will be determined by such factors as viscosity and temperature of feed stock, percent lter aid added, percent lter cake removed, and the like.

The iiltrate removed may be separated into its component layers in any conventional type of settling apparatus adapted to the.A practice of this invention, or in a conventional centrifuge. The filtrate is preferably settled, without unnecessary agitation since it' has been found that prolonged agitation decreases the settling rate by as much as 50%. This settling operation is: preferably carried out at slightly elevated temperatures although settling at room temperature may be desirable in some cases. The data shown A in Table l was determined inv a B-inch pipe having a 9-foot liquid column` The data shows the tremendous advantage obtained in rate kof settling by treating the tar bythe process of this The dilute acid layer may be concentrated and reused in the acid treatment of other stocks, it may be utilized asis or treated in. any desired manner. acid layer may be discarded'.

The' small. amount of acidity remaining* in separated. tar may be conveniently. neutralized with afdilute alkaline solution. Aqueous caustic yis very well adapted to this neutralization. A

concentration of between about 1% and 10% aqueous. sodiumhydroxide has been found' satisfactory for this neutralization.

The neutralized. tar may be settled andthe tar `layer .removed from the aqueous salt layer. A settling aid may be employed if-desirableto assist 'in this settlingvoperation. The degree of settling requiredWill-depend onthe allowable ash content of the nal acidfreetar.

Tar removable from. the neutralization settling f' tank is fed to thev distillation column where the bulk olf. .the solvent is read-ily removed by vatmospheric distillation. The remainder f. the solvent is recovered by distillation undervacuum or with: steamA if further recoveryl is desirable. 1`he-f1'.eeoveredI solvent maybe recirculatedin the process` indefinitely, it being only necessary to make. upwithL a small amount oi solvent for unavoidable losses.

A iinal acid free tar produced by this` .process i has; .the appearance andv lmany of.: the uses of asphalt. Lt is a good fuel, both by itself and mis-edgwth. cracked tarv and cutter. and may be 'usadas a fuel-in many applications and without theusual corrosive effect and fume nuisance .of'

`an acid tar.

' The. following examples .are given for illusltrat'ivepurposes only,and, are not' tjobe taken as limiting, the. invention to the precise details set "forth,

If' vutilization is not attractive,- the Example 1.-A tar emulsion produced by the hydrolysis of a cracked naphtha sludge, and containing about H2SO4 is mixed with a solvent c'onsisting of a mixture of aromatic hydrocarbons boiling in the range of S40-470 F. to give a mixture containing '70% by volume of solvent. Filtration is carried out in a rotary precoat 'lter adding 0.8% (by 4weight of tar) of Celite filter aid which consists of diatomaceous silica.

The lter is run at 47.3 revolutions per hour and at 110 F. A rate of 4.12 barrels of tar per day v per square foot of nlter area is maintained. The

filtrate is settled in a tank at F. The settling rate. is 21.95 feet per hour and the tar layer .Y' separated contains 0.42% by .weight sulfuric drawn and subjected to atmospheric distillation.

92% of the solvent in the tar is thus recovered, the remainder being removed by steam-distillation. Substantially acid free tar is recovered from the still pot.

Example 2;-A composite sample of emul'sified tar produced by the hydrolysis of cracked naphtha sludge, straight run gasoline sludge, vand reformed' naphtha sludge and containing about 15% H2804, is diluted with the 'solvent of Ex'- ample 1 to give a mixture having 60% by volume solvent. The mixture is filtered at 'the rate of 6.73 barrels of tar per day per square footfof lter area under the conditions of Examplel 1. The nitrate is settled in the aforementionedtank vat a rate oi' 1.0.0 feet per hour and contains less than 0.5% sulfuric acid. The settled tar layer is removed, neutral-ized, and distilled as before; of the solvent in the tar is recovered by atmospheric distillation and theremainder is recovered., by vacuum distillation. Acid -free tar is removed from the still pot.

While the character of this invention has been described in some detail and illustrations have been vgiven of the. use of this process, it is tube understood that the invention in itsbroader as,- pects is not limited thereto but includes modiiications andvariations within the scope of the ap;- pended claims. I claim: 1'. A process for producing acid-free tar from an emul'siiied acid tar derived by hydrolyzi'ngfin the` presence Vof water and steam an acid sludge resulting from the treatment with sulfuric acid'of a. petroleum stock` boiling in the boiling range of gasoline and kerosene to produce andvseparatje thereby .a dilute acid layer and a layer 'compris- `ing said emulsied acid tar, which. comprises mixing the emulsied acid tar with a `solvent therefor consisting predominantly ofv a mixture lof..aromatic.hydrocarbonsYboiling in the range of aboutl340 to 41.7.0" .adding a. small amount of diatomaceous silica filter aid to the. resulting mixture and then passing it through aiiltenper.-

mitting the iiltrate tosettle whereby .it separates -into an upper relatively acid-free tar layer anda lower relatively acid rich aqueous layer, separatingthe two layers and neutralizingresidual acid in the tar layer with caustic, subjecting4 the neutralized. tar Vto `distillation to separate the solvent and to recover acid-free tar as a product.

2. The process as defined in .claiml 1`v wherein the emulsifled acid tar is obtained by hydrolyaing an acid sludge resulting from the treatment of cracked naphtha with sulfuric acid.

3. The process'as defined in claim l'wherein the emulsifled acid tar is obtained by `hydroiyzing 5 6 an acid sludge resulting from the treatment of UNITED STATES PATENTS reformed naphtha with sulfuric acid.

4. The process as defined in claim 1 wherein Number Name Date the emulsied acid tar is obtained by hydrolyzing 1,271,387 Taveau July 2, 1918 an acid sludge resulting from the treatment of 5 1,973,118 Spencer Sept. 11, 1934 straight run gasoline with sulfuric acid. 2,228,527 Meyer Jan. 14, 1941 ROBERT J. MILLER. 2,301,335 Showalter Nov. 10, 1942 2,320,242 Kok-altnur et al. May 25, 1943 REFERENCES CITED The following references are of record in the lo le of this patent: 

